The landslide, which struck the E6 highway in Stenungsund, 50 kilometres north of Sweden’s second-largest city Gothenburg, ripped up a petrol station car park, overturned lorries and caved in the roof of a fast food restaurant.

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Prosecutor Daniel Veivo Pettersson said on Thursday he believed “human factors” were behind the landslide as “no natural cause” had been found during the investigation.

He told a press conference the landslide had been triggered by a nearby construction site where too much excavated material had been piled up, putting excessive strain on the ground below. 

“At this stage, we consider it negligent, in this case grossly negligent, to have placed so much excavated material on the site,” Pettersson said.

Pettersson added that three people were suspected of among other things gross negligence and causing bodily harm, adding that the investigation was still ongoing.

The worst-hit area covered around 100 metres by 150 metres, but the landslide affected an area of around 700 metres by 200 metres in total, according to emergency services.

Three people were taken to hospital with minor injuries after the collapse, according to authorities.